There is a need for containers allowing detection of spoilage of the packaged fluids during storage. It would further be desirable to detect spoilage using non-destructive methods and without opening the package. Such methods would be even more advantageous for products which are aseptically filled such as nutritional or health care compositions or compositions intended for particularly sensitive people, such as for example infants.
DE 100 22 177 B4 discloses a means for signaling the state of a liquid contained in a bottle consisting of a cap having a transparent top and equipped with a flexible membrane that is deflected when the container is closed due to the internal pressure present in the bottle and subsequently in a flat position after the bottle has been opened. The visual aspect of the top surface of the membrane is different when the flexible membrane is deflected from the visual aspect of said upper surface of the flexible membrane when it is in a flat position, thus allowing visual identification of the state of the content. The system described in this document is mainly useful for bottles containing carbonated beverages which create a higher pressure inside the container than outside when the bottle is closed and the content is carbonated (deformed membrane), whereas the membrane is flat when the liquid is de-carbonated or the container has been opened. However, this cap is not suitable for aseptically filled content and is therefore not suitable to solve the above problem.